Retrofit filtration system



FIG. 1 is a perspective view of a retrofit filtration system according to my novel design, said retrofit filtration system shown in environmental on a portable water tank, the broken line representation of said portable water tank shown for illustrative purposes only forming no part of the claimed design;

FIG. 2 is a front elevational view, thereof;

FIG. 3 is a rear elevational view, thereof;

FIG. 4 is right side elevational view, thereof, the left side elevational view thereof being a mirror image;

FIG. 5 is a top plan view, thereof; and,

FIG. 6 is a bottom plan view, thereof.

The portable water tank showing the article in environment in FIGS. 1 through 5, inclusive, shown in said Figures in broken lines is included solely for illustrative purposes, and forms no part of the claimed design. 

The ornamental design for a retrofit filtration system, as shown and described. 